Stabilization of peracids with picolinic acid



United States Patent Oice 3,192,254 srAnrLrzArroN on PERACIDS wirn rrcorrNic ACID Ernest R. Hayes, Shawinigan South, Quebec, Canada,

assignor to Shawinigan Chemicals Limited, Montreal,

Quebec, Canada, a corporation of Canada No Drawing. Filed Get. 19, 1959, Ser. No. 847,080 8 Claims. (Cl. 260502) tion of acetaldehyde in a non-reactive organic solvent in presence of a metal compound catalyst is extremely unstable at room temperature or at higher temperatures. It the unstabilized crude is allowed to come to room temperature, it will start to decompose exothermically and boil quite rapidly. Thus, the unstabilized crude cannot be stored except at low temperatures; otherwise it must be rectified immediately. Furthermore, the unstabilized crude decomposes While being rectified and may create an explosion hazard. Even known peracid stabilizers such as dipicolinic acid have little or no efiect on the stability of such crudes.

It is. an object of the present invention to provide an effective stabilizer for peracetic acid solutions in a nonreactive organic solvent.

It is also an object of the present invention to provide an effective stabilizer for both refined peracetic acid and crude peracetic acid containing, for example, acetaldehyde, traces of metal catalyst, or acetic acid.

It is also an object of the present invention to provide a stabilizer for both refined and crude peracetic acid which is effective at elevated-temperatures.

Other objects and advantages of the present invention will appear from the description to follow.

The invention broadly consists in a method of stabilizing a carboxylic peracid which comprises incorporating picolinic acid therein.

The invention also consists in a composition of matter comprising a lower molecular weight carboxylic peracid and a stabilizing amount of picolinic acid.

3,i%2,254 Patented June 29, 1965 .tive for stabilizing such crude acid solutions, in contrast to dipicolinic acid which has very little stabilizing effect on the crude. It was found that picolinic acid is also very effective for stabilizing refined peracetic acid in a non-reactive organic solvent solution.

Picolinic acid, technically i-pyridine carboxylic acid, diiiers from dipicolinic acid, 2,6-pyridine dicarboxylic acid, by having only one carboxylic acid group in its molecule in the position on to the nitrogen atom while dipicolinic acid has two such groups, in the cc and or. positions respectively. Since the mechanism of peracid stabilization is not clear, one could not predict that the compound having one carboxylic group on the pyridine nucleus would be a stabilizer merely because the compound having two carboxylic groups on the same nucleus is a stabilizer. Still less could one predict that the reduction from two groups to one would result in a more effective stabilizer.

The amount of picolinic acid to be added as stabilizer may vary widely, depending on the stability desired in the product and on the magnitude of the factors contributing to the instability of the material. These factors include (a) the natural instability of peracetic acid, which is uniform at a specific temperature in the absence of other factors, the presence of metal ions, (0) the presence of acetaldehyde, and (d) the temperature of the solution. Useful amounts are up to 1000 parts per million of solution, by weight. Generally, 250 to 750 parts per million are suflicient to ensure good stability.

EXAMPLES The following examples, in which ppm. denotes parts per million, are illustrative of the invention. In these examples, room temperature defines a temperature of C., and the percentages given are by weight.

Example 1 Three samples of 100 cc. each of a peracetic acid solution in ethyl acetate were isolated in polyethylene bottles. The peracetic acid solution contained 7.71% peracetic acid, 1.8% acetic acid, 0.7% acetaldehyde, 0.1-0.5 organic peroxide, 0.005% CoCl .6H O, and balance ethyl acetate. 500 ppm. of picolinic acid were added to one sample while 500 p.p.m. of dipicolinic acid were added to the second one. The third 100 cc. sample was retained as reference. The three samples were loosely stoppered and stored at room temperature. The peracetic acid content of the samples was determined with the following results:

PERCENT PERACID AFTER ELAPSED TIME Time (hrs) Stabilizer 1 2 26 122 146 170 194 218 290 314 Picolinie acid 6. 4. 4. 32 4. l0 3. 3. 90 3. 70 3. 50 2. 20 l. Dipicolime acid... 6. 26 3. 90 3. 06 1. 50

Reference 1 Discarded after 122 hours. Discarded when it began to decompose vigorously in the interval l-2 hours.

Example 2 Three samples of cc. each of a peracetic acid solution in methyl acetate were isolated in polyethylene bottles. The peracid solution analyzed 7.4% per-acetic acid, 1.2% acetic acid, 1.4% acetaldehyde, 0.-1-0.5% organic 7O peroxide, 0.005% CoCl .6H 0, balance methyl acetate.

The three samples were treated with 100, 500, and 1,000 ppm. picolinic acid respectively, and stored at room tem- A crude peracetic acid solution in ethyl acetate was tested for stability at elevated temperature. The crude analyzed 7.4% peracetic acid, 0.9% acetic acid, 1.8% .acetaldehyde, between 0.1 and 0.5% organic peroxide, traces of CoCl .6H O, and balance ethyl acetate. TW samples of 66 cc. each of this crude were isolated in loosely stoppered polyethylene bottles, and stabilized with 500 ppm. of picolinic acid (0.33 ml. of solution in acetic acid, 0.1 g. per ml.) and dipicolinic acid (1.66 ml. of solution in acetic acid, 0.02 g. per ml.; prepared by heating the acetic acid to accelerate rate of solution), respectively. The two stabilized samples were brought to 45- 50 C. and maintained at that temperature for four hours, then stored at room temperature. They were periodically analyzed for peracetic acid content. The results were as follows:

Percent peracid after elapsed time Stabilizer hours hours hours 1 hours 2 Picolinic acid 7. 4 4.1 4. (J 4.1 4. 0 Dipicolinic acid 7. 5 3. 5 3. 4 3. 4 3. 3

1 This period included 65 hours at room temperature. 1 This period included 89 hours at room temperature.

Example 4 PERCENT PERAOID AFTER ELAPSED TIME The foregoing examples are given by way of illustration only, and do not limit the scope of the invention. Thus other peracids, for example perpropionic acid, can be stabilized with picolinic acid. It is preferred to use picolinic acid as the pure acid. However, salts of picolinic acid which are soluble in the solvent used can also serve as stabilizers.

It will be understood that many other variations of this process may be made without departing from the invention which is as defined in the following claims.

I claim:

1. A composition of matter comprising peracetic acid, in at least one solvent for peracetic acid selected from the group consisting of acetic acid, methyl acetate, and ethyl acetate, and a stabilizing amount of picolinic acid.

2. A composition of matter according to claim 1 in which the picolinic acid is present in an amount of up to one thousand parts per million of solution.

3. A process for stabilizing peracetic acid in solution in at least one solvent for peracetic acid selected from the group consisting of acetic acid, methyl acetate, and ethyl acetate which comprises incorporating a stabilizing amount of picolinic acid in said peracetic acid solution.

4. A process as claimed in claim 3, in which the peracetic acid solution is crude peracetic acid prepared by oxidation of acctaldehyde with an oxygen containing gas in said solvent and in the presence of a metal salt catalyst of the group consisting of salts of cobalt and copper.

5. A process according to claim 3, in which the organic solvent is ethyl acetate.

6. A process in accordance with claim 3 in which the solvent is acetic acid.

"7. A process according to claim 3 in which the solvent is methyl acetate.

3. A process according to claim 3 in which the picolinic acid is present in an amount of up to one thousand parts per million of solution.

References Qited by the Examiner UNITED STATES PATENTS Re. 25,057 lO/6l Stevens.

2,347,434 4/44 Reichert et al. 2,609,391 9/52 Greenspan et al. 260502 2,624,655 1/53 Greenspan 237207.5

FOREIGN PATENTS 716,077 9/54 Great Britain.

LORRAINE A. WEINBERGER,

Acting Primary Examiner.

LEON ZITVER, CHARLES B. PARKER, Examiners.

1 This sample was discarded after 428 hours. 

1. A COMPOSITION OF MATTER COMPRISING PERACETIC ACID, IN AT LEAST ONE SOLVENT FOR PERACETIC ACID SELECTED FROM THE GROUP CONSISTING OF ACETIC ACID, METHYL ACETATE, AND ETHYL ACETATE, AND A STABILIZING AMOUNT OF PICOLINIC ACID. 